Returns the value of a system metric, or -1 if the metric is not supported on the current system.

The value of win determines if the metric returned is a global value or a wx.Window based value, in which case it might determine the widget, the display the window is on, or something similar. The window given should be as close to the metric as possible (e.g. a wx.TopLevelWindow in case of the wx.SYS_CAPTION_Y metric).

win is a pointer to the window for which the metric is requested. Specifying the win parameter is encouraged, because some metrics on some ports are not supported without one,or they might be capable of reporting better values if given one. If a window does not make sense for a metric, one should still be given, as for example it might determine which displays cursor width is requested with wx.SYS_CURSOR_X.